Join Date: Aug 2007
Location: Gone my own way
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Something to dial into your thinking is that when E-10 or RFG/E (reformulated gasoline w/ 10% ethanol) is subject to water contamination above 0.4%, the ethanol breaks its bond with the gasoline and mixes with the water. When that happens, the three octane points that the ethanol adds to gasoline is gone. Thus, someone pinching on fuel grade may find that their 89-octane is really only 86 if water contaminated. A drop from 91 to 88 may be livable for a while, but 86 may be beyond the range that the ECU can accommodate. 87 to 84 certainly will be. 0.4% water isn’t that much; I would buy from a reputable dealer with enough volume turnover so his tanks are kept clean and condensation or rainwater-free.
The 10% ethanol reduces the efficiency of the gasoline about 2%.
Last edited by Old smart; 02-21-2008 at 10:07 AM.